weird optimization in sin+cos, x86 backend

[Andrew Haley]

On 02/09/2012 01:38 PM, Tim Prince wrote:
> x87 built-ins should be a fair compromise between speed, code size, and 
> accuracy, for long double, on most CPUs.  As Richard says, it's 
> certainly possible to do better in the context of SSE, but gcc doesn't 
> know anything about the quality of math libraries present; it doesn't 
> even take into account whether it's glibc or something else.

Yeah.  On x86_64 glibc, we should really get the sincos bg fixed.  And
it really is a bug: cos() and sin() are correctly rounded but sincos()
isn't.

Andrew.